Previously work has shown that infarct size following acute coronary occlusion in the chronically sympathectomized heart is much less than in controls or acutely sympathectomized hearts. This effect may be due to a reduced myocardial oxygen demand and to an increased ischemic perfusion. The proposed studies are designed to: (1) characterize the oxygen consumption of the sympathectomized heart over a wide range of afterloads and to compare the relationship to that in controls. (2) To further verify the reduction in infarct size by using independent techniques to assess infarct size. These include determination of CPK and S-T elevation in control and sympathectomized hearts.